Guanglei Wu

In situ synthesis and preparation of TiO2/polyimide composite containing phenolphthalein functional group

In this paper, titanium dioxide (TiO2)/phenolphthalein-type polyimide (PPPI) composite was synthesized in situ polymerization, the diamino phenolphthalein type compound and dimethylacetamide as the matrix, and TiO2 as the filler. The mechanical property and thermal conductivity properties were used to characterize the properties of the obtained composite. A diamine monomer containing more benzene rings of phenolphthalein and an ether bond in its main chain were prepared, synthesized by a nucleophilic substitution reaction and a hydrazine hydrate reduction reaction. Polyimide composite had the same structure as that of a diamine monomer. And it was synthesized by solution imidization and heat imidization. The results showed that TiO2 improved the dispersibility, alignment and interfacial strength of the TiO2/PPPI composite. The mechanical property of polyimide composite was increased with the increasing TiO2 loading. And a suitable addition of TiO2 could enhance the mechanical properties of polyimide system. Compared to polyimide resin, the TiO2/PPPI composite had a higher thermal conductivity with the increasing of TiO2 content. All of these changes in properties were closely correlated with the TiO2/PPPI composite, which could form an interaction interface structure in the system.

Synthesis and Properties of Semicrystalline Copolyimides Based on 4,4′-Diaminodiphenylether and 1,3-Bis(4-aminophenoxy) Benzene

Copolyimides were prepared from 4,4′-diaminodiphenylether (4,4′-ODA), 1,3-bis(4-aminophenoxy) benzene (TPER), and pyromellitic dianhydride (PMDA) through a three-step imidization process with different monomer compositions. The copolymerization disrupted the molecular regularity and decreased the intermolecular interaction of the polyimide chains. The X-ray diffraction (XRD) results indicated the prepared copolyimides showed the same semicrystalline character, but had various crystallinity and crystal forms. The copolymerization also changed the crystal morphologies of the polyimides. With increasing TPER ratio, the copolyimides started to form spherulites and hedrites, which then tended to grow more perfectly as the TPER ratio was further increased. The solubility of the copolyimides and their dependence on the crystallnity and the chain flexibility was investigated. These copolyimides exhibited excellent thermal and thermo-oxidative stability.

Preparation and properties of Nano-SiO2/TDE-85/BMI/BADCy composites

A new type of the nanometer particles and epoxy/bismaleimide-triazine nanocomposites were prepared using a nanometer silica (nano-SiO2), a 4,5-epoxycyclohexane 1,2-dicarboxylic acid dilycidyl (TDE-85) epoxy resin, a 4,4′-bismaleimidodiphenymethane (BMI) and a bisphenol a dicyanate (BADCy). The properties of nano-SiO2/TDE-85/BMI/BADCy composites, such as mechanical and thermal properties, were systemically investigated in detail by mechanical measurement, scanning electron microscope (SEM), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The experimental results showed that the addition of the appropriate amount of nano-SiO2 could improve the impact strength and the flexural strength of the nano-SiO2/TDE-85/BMI/BADCy composites. Simultaneously, the thermal stability of the blends was found to be higher than that of the TDE-85/BMI/BADCy copolymers.

Synthesis and Characterization of Novel Sulfone-containing Polyimides Molding Powder Derived from 2, 2-Bis[4-(4-aminophenoxy) phenyl] Sulfone and Aromatic Dianhydrides

A novel sulfone ether diamine was successfully synthesized by aromatic nucleophilic chloro-displacement reaction of 4-chloronitrobenzene with the 4, 4′-dihydroxydiphenylsulfone, followed by a catalytic reduction. Two kinds of aromatic polyimides molding powder containing sulfone and ether linkages was prepared from the resulting diamine with pyromellitic dianhydride (PMDA) and benzophenonetetracarboxylic dianhydride (BTDA) by a new three-step imidization procedure. The monomer and polyimides powder obtained were characterized by various methods. The monomer was synthesized with high purity and yield. The novel polyimides powder exhibited semi-crystalline character, good solubility in organic solvents, as well as high Tg value and excellent thermal stability in N2 and air.

Synthesis, characterization, and thermal properties of benzoxazine monomers containing allyl groups

The polymerization mechanism of allyl-functional benzoxazine (Bz) monomers is reported in this article. Following the traditional route of Bz synthesis, a series of monofunctional Bz monomers were synthesized via allylamine and amine condensation reaction with 2,2′-diallyl bisphenol-A and paraformaldehyde. Resulting chemical structures of the synthesized monomers were confirmed by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance analyses. The polymerization behavior of the prepared allyl-functional monomers was studied using differential scanning calorimetry and FTIR. Three reactions were observed in the curing process: polymerization reaction of N-allyl groups in the oxazine ring, ring-opening polymerization of Bz, and polymerization reaction of allyl groups in benzene. Compared to a typical polybenzoxazine (PBz), higher cross-linking density in PBz-allyl-2 leads to a higher glass transition temperature and 5% weight loss temperature, which indicates improved thermal stability in PBz-allyl-2 as well as superior thermal conductivity compared to 2,2′-bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl)propane. Data on dielectric properties also show that PBz-allyl-2 outperforms typical PBzs. This work focuses on the manipulation of Bz monomer structures to alter their ring-opening polymerization mechanism, as well as cross-linking, in order to derive a PBz with improved properties.